ARS occurs following acute exposure to very high levels of radiation, and involves severe, potentially lethal injury to the bone marrow as well as to other organs and systems within the body. High doses of radiation can destroy the bone marrow’s ability to produce white cells, red cells and platelets; without these cells patients are at high risk of death.

The study was designed to assess the safety and efficacy of Pluristem Therapeutics’ PLX-R18 following intramuscular injection into irradiated and non-irradiated non-human primates (NHPs). Efficacy measures included survival as well as level of bone marrow function, which is affected by exposure to high levels of radiation as may occur in a nuclear accident or attack.

While this pilot study was not powered to demonstrate statistical significance, all cohorts treated with PLX-R18 showed improved survival compared to cohorts that received placebo. The two lower dosages, 4 and 10 million cells per kilogram body weight, resulted in an 85% survival rate in irradiated NHPs compared to a 50% survival rate in the placebo treated control group.

This pilot study also demonstrated a trend towards enhanced neutrophil and lymphocyte recovery.

No serious adverse reactions were observed in non-irradiated NHPs, suggesting that in scenarios requiring the rapid treatment of large populations, such as in the case of a nuclear emergency, no determination of an individual’s level of exposure would be required prior to treatment.

These data will help inform a pivotal study designed to meet the requirements for a Biologics License Application (BLA) submission under the FDA’s Animal Rule regulatory pathway.

“The transition from small to large animals has always been a challenge in therapeutic product development, and the success of this study marks a significant milestone. Our unique, multifactorial PLX-R18 cell therapy was developed to repair the body’s ability to

produce all three blood lineages in a timely manner,” said Zami Aberman, Co-CEO and Chairman of Pluristem. “This therapy would protect patients from severe infection, anemia and hemorrhage, saving lives in the case of a nuclear event.”

Pluristem leadership expressed their interest in pursuing further support of PLX-R18 development with U.S. government agencies. “We are confident that PLX-R18 can serve as a powerful tool for governments to protect their citizens against the devastating health impact of potential exposure to nuclear radiation,” noted Yaky Yanay, CoCEO and President of Pluristem.